elworthy



Dec. 26, 1961 B. c. T. ELWORTHY 25,104

SAFETY SYSTEM FOR SAWMILL CARRIAGES 4 Sheets-Sheet 1 Original Filed Feb.10, 1958 INVENTEOR. Bernard CI Elworfiy 1961 B. c. T. ELWORTHY Re.25,104

SAFETY SYSTEM FOR SAWMILL CARRIAGES 4 Sheets-Sheet 3 Original Filed Feb.10, 1958 Om\ 2 O UXQQEFMW INVENTOR. Bernard CT Elwopih Hgen i- 7 Re.25,104 Reissued Dec. 26, 1961 United States Patent Ofiice SAFETY SYSTEMFOR SAWMILL CARRIAGES Bernard C. T. Elvv'orthy, Vancouver, BritishColumbia,

Canada, assignor to Elmer R. Worth, Sr., Salem, Oreg. Original No.2,893,448, dated July 7, 1959, Ser. No.

714,325, Feb. 10, 1958. Application for reissue Mar.

31, 1960, Ser. No. 19,137

14 Claims. (Cl. 143120) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

This invention pertains to the operation of sawmill carriages, andrelates particularly to a safety system by which the operatingcomponents of a sawmill carriage are prevented from entering the sawline.

The construction and operation of a sawmill carriage and saw assemblybriefly is as follows:

The carriage is a wheeled framework supported upon spaced rails whichguide the carriage back and forth past a power driven saw. The carriageincludes a plurality of spaced head blocks upon each of which a knee ismounted for lateral reciprocation, i.e. toward and away from the sawline of a saw which is mounted adjacent the carriage. The knees may bereciprocated by various means such as hydraulically actuated rams or,more conventionally, by rack and pinion or sprocket and chain connectionto a rotary set shaft which is driven by an electric motor or otherelectrically actuated motor such as an air or hydraulic type motor.Control of the movement of the knees in desired increments toward thesaw line is provided by jog switch or, more accurately, by setworks.Logs are deposited one at a time from a log deck upon the head blocks ofthe carriage in abutment with the faces of the knees. The log isretained in this position by such means as tong dogs and hook dogs, wellknown in the art. The hook dog generally is em-' ployed to secure largerlogs and cents against the knee and the tong dogs generally' areemployed to secure smaller logs and cants.

In addition, provision generally is made for moving each knee withinrestricted limits independently of the setting motion provided by thehydraulic rams or set shaft drive. This provision is made to compensatefor the normal taper of a log in order to align the longitudinal axis ofa log parallel to the saw line preliminary to removing the surfaceslabs.

In the normal operation of a sawmill carriage it frequently' occurs,through inadvertence or faulty operation of the apparatus, that the kneeitself or the dogs supported thereby are moved forwardiy into the sawline where they may be engaged by the saw. This situation not onlypresents an extremely hazardous condition to the operators, but alsoresults in serious damage to the saw andto the operating components ofthe carriage, necessitating costly repairs and loss of operating time.

Accordingly, it is a principal object of the present invention toprovide a safety system by which to prevent the knees and dogs supportedthereby from entering the saw line.

Another important object of this invention is the provision of a safetysystem by which the limit of forward movement of the knees of thesawmill carriage is determined automatically by the condition of taperof the knees, or by the'position of extension or retraction of the dogsassociated with the knees.

A further important object of the present invention is riages, and whichis capable of long and faithful service with a minimum of maintenanceand repair.

The foregoing and other objects and advantages of this invention willappear from the following detailed description, taken in connection withthe accompanying drawings, in which:

FIG. I is a fore-shortened end view, partly in section, of a sawmillcarriage illustrating an operational arrangement for a knee andassociated dogs, and adaptable for control by the safety system of thepresent invention;

FIGS. 2 to 7 inclusive are schematic plan views of a sawmill carriageassembly and illustrating various conditions of operation andcorresponding requirements for control by the safety system of thisinvention;

FIG. 8 is a plan view of a control assembly forming a part of a safetysystem embodying the features of the present. invention;

FIG. 9 is a' sectional view taken along the line 99 of FIG. 8 andillustrating the manner of adjustment of the switch support betweenconditions of taper and no, taper of the knees of a sawmill carriage;

FIG. 10 is a fragmentary sectional view taken along the line 10*10 inFIG. 9;

FIG. 11 is a sectional view taken along the line 1111 in FIG. 8; f

FIG. 12 is a sectional view taken along the line 12-12 in FIG. 11 andshowing a structural arrangement for a cam assembly forming a part ofthe control assembly of FIG. 8; v FIG. 13 is a schematic diagram of anelectric circuit adaptable for use with the control assembly of FIG. 8and the carriage assembly of FIG. 1; and

FIG. 14 is a schematic diagram of an electric circuit adaptable for usewith a modified form of control assembly.

' Referring to FIG. 1 of the drawings, the sawmill carriage assemblyillustrated therein includes a carriage frame 20 provided with aplurality of rollers 22 supported upon spaced tracks 24 whichaccommodate movement of the carriage in a direction parallel to a sawline base is connected to an endless chain 32 which is reeved overspaced sprockets.-- The forward sprocket 34 is mounted for rotation onashaft 36 journaled adjacent the forward end of the head block, and therearward sprocket 38 is secured for rotation with a set shaft 40journaled for rotation adjacent the rearward end of the head block. Theset shaft is coupled in any conventional manner to a source of power. Inthe embodiments illustrated in FIGURES l3 and 14, the set shaft 40 iscoupled through sprockets 42, 44 and chain 46 to the drive shaft 48 ofthe reversible electric motor 50.

A knee structure is associated with the knee base in any conventionalmanner. In the embodiment illustrated in FIGURE 1, the knee structure isa hollow member formed by spaced side walls 52 interconnected by a rearbrace 54, a top brace 56, and a front plate 58. The knee is supportedslidably upon the headblock and the rear brace thereof is connected tothe knee base by such means as the adjustable assembly of the taper aircylinder 60 and piston 62. It is by means of this adjustableinterconnection that the knee may bemo'ved relative to the knee base toaccommodate the taper mentioned heroin before.

Within the hollow structure of the knee is a tong dog support 64,arranged for forward and rearward reciprocation with respect to thefront plate of the knee. In the embodiment illustrated the dog supportis mounted upon one arm 66, 68 of each of a pair of hell crank membersby means of pins 70, 72 which project from said bell crank membersthrough elongated slots 74, 76, respectively, in the dog support. Thebell crank members are mounted pivotally intermediate their ends on aside wall of the knee structure, as by means of the pins 78, 80. Theopposite arms 82, 84 of the bell crank members are inter connectedpivotally by the link 86. The terminal end of the bell crank arm 82 isconnected pivotally to the piston rod 88 associated with the tong dogsupport air cylinder 90 which is mounted pivotally at its opposite endon the side wall of the knee structure, as by means of the pivot pin 92.

Thus, by actuation of the tong dog support cylinder to extend its pistonrod, the bell crank members are pivoted in a clockwise direction,whereupon the tong dog support is moved rearwardly with respect to thefront wall of the knee structure. Conversely, when the tong dog supportair cylinder is actuated to retract its piston rod, the bell crankmembers are pivoted in a counterclockwise direc tion to move the tongdog support forwardly toward the front wall of the knee stucture.

Mounted slidably for vertical reciprocation on the tong dog support is atong dog air cylinder 94. A lower tong dog 96 is secured to the lowerend of this cylinder and projects forward and upward through alongitudinal slot in the head block for limited vertical reciprocation.A piston rod 98 projects from the opposite end of the air cylinder andsupports an upper tong dog 100 which projects arcuately forward anddownward, in opposition to the lower tong dog. A slot 102 is formedbetween the top brace and the front plate of the knee to accommodateextension of the upper tong dog therethrough.

' Thus, by actuation of the tong dog cylinder in the direction to drawthe opposed tong dogs together, the upper tong dog is moved downwardlyinto engagement with the upper surface of a cant 103 supported on thehead blocks. As this dog tends to move further downward, the tong dogair cylinder is moved vertically, elevating the lower tong dog intoengagement with the lower surface of the cant.

Also mounted on a side wall of the knee support on pivot pin 104 is ahook dog 106 which extends upwardly through the slot 102 in the knee. Anextension 108 on the hook dog is pivotally connected to the piston rod110 of the hook dog air cylinder 112, the opposite end of the latterbeing secured pivotally to the side wall of the knee by means of 'thepivot pin 114.

Thus, by actuation of the hook dog cylinder to extend its piston rod,the hook dog is pivoted in the clockwise direction to project the hookforwardly and downwardly to engage a log positioned on the head blocks.

From the foregoing'it will be apparent that there are several conditionsof operation of the knees and dogs in the normal operation of a sawmillcarriage assembly, each of which presents a different safety situationin connection with the saw line. These conditions are illustratedschematically in FIGURES 2 to 7, inclusive, wherein the carriage 20 isshown to include three head blocks 28 and knees 52, each having a tongdog assembly and the center knee only having a hook dog assembly. InFIGURE 2 the illustration exemplifies the situation wherein the kneesare not tapered and none of the dogs are extended, such as might be thecase when a log or cant 103 is being rejected from the carriage or whenthe final board is being removed from the carriage. FIGURE 3 illustratesthe condition in which a cant is being held against the knees by thetong dogs only, and the knees are not tapered. FIG- URE -4 illustratesthe condition in which a tapered log 115 is resting freely againsttapered knees and is to be rejected from the carriage. FIGUREillustrates the condition in which a tapered log is secured againsttapered knees by means of the tong dogs, preliminary to removing thesurface slabs. FIGURE 6 illustrates the condition in which a log or cantis held against untapered knees by means of the hook dog as well as thetong dogs, as is sometimes required with cants of large dimension.FIGURE 7 illustrates the condition in which a tapered log is supportedagainst tapered knees by means of the hook dog and, if practicable, thetong dogs as well.

It will be apparent from the illustrations in FIGURE 2-7 inclusive, thatthe minimum safe distance between the front face of the knee and the sawline must be varied, depending upon the condition of taper and theposition of extension or retraction of the tong and hook dogs, toprevent any of said components from entering the saw line. It is thecontrol of this minimum distance that the safety system of the presentinvention achieves, by means of an assembly of switches and switchactuators arranged in such manner as to stop the forward movement of theknees when the forwardmost projecting component of the knee assemblyreaches a predetermined safe position with respect to the saw line.

Referring now to FIGURE 13 of the drawings, wherein is illustratedschematically one embodiment of the safety system of this invention, thereversible set shaft motor 50 is connected through forward and reversestarter switch assemblies 116 and 118, respectively, to the lines L1, L2and L-3 leading to a source of electrical potential. These forward andreverse switches are controlled selectively by means of forward andreverse relays 120 and 122 respectively. The reverse relay is includedin an electric circuit from line L2 through the reverse control pushbutton switch 124, through the reverse safety switch 126 and theemergency stop switch 128, to line L-1. The forward relay is included inan electric circuit extending from line L-2 through either the forwardjog push button switch 130 or a setworks mechanism 132, and thenceselectively either through the hook dog safety switch 134, or throughthe series arrangement of the forward safety switch 136 and the normallyopen switch 138 of relay 140 and the normally closed switch 142 of relay144, or through the series combination of the tong dog safety switch 146and the normally closed switch 142 of relay 144. From any of thesealternate paths the circuit is completed through the emergency stopswitch 128 to line .L-l. The path through which the forward relay iscompleted depends upon the position of extension or retraction of thetong dogs and hook dog, as follows:

The valve 148 controlling the air to the tong dog support cylinder 90 iscontrolled by the solenoid 150 which is arranged in an electric circuitextending from line L-2 to the tong dog push button switch 152 to lineL-1. In the normally open position of this push button switch, the aircontrol valve is positioned to supply air to the tong dog supportcylinder in such manner as to move the dog support forwardly toward thefront plate of the knee, whereby to maintain the tong dogs extended fromthe front face of the knee, as illustrated in FIGURE 1. When the tongdogs are to be retracted into the knee, the tong dog push button switch152 is closed to complete the electric circuit of the solenoid 150,thereby simultaneously completing the circuit of relay 140 and closingthe normally open switch 138. Thus, the electric circuit of the forwardrelay 120 is completed through all three of the safety switches 134, 136and 146. However, as explained more fully hereinafter, the forwardsafety switch 136 will be opened last of the three by virtue of thearrangement of safety switch actuators, thus permitting the knee toreach a position of minimum distance from the saw line.

When the tong dogs 96, 100 are extended by opening the tong dog pushbutton switch 152, relay 140' is deenergized and the associated switch138 is opened. Thus the electriccircuit of the forward relay 120 iscompleted only through the hook and tong dog safety switches 134 and146, respectively, and, as explained hereinafter, since the tong dogsafety switch will be opened after the hook dog safety switch, theforward movement of the knee will be arrested at a point farther removedfrom the saw line, in order to prevent the extended tong dogs fromentering the saw line.

The hook dog 1-06 is extended by closing the hook dog push button switch154, [then by] thereby completing an electric circuit from line L1through the hook feed safety switch 156, through the relay 158 to lineL-2. Upon energization of this relay, the normally closed switch 160 inthe circuit of the hook dog retraction solenoid 162 is opened and thenormally open switch 164 in the circuit of the hook dog extensionsolenoid 166 is closed, thereby actuating the air control valve 168 tothe position in which the hook dog air cylinder 112 is actuated toextend the hook dog. Simultaneously, closure of the normally open switch164 causes energization of relay 170 and closing of its associatednormally open switch 172, thus energizing relay 144 and opening thenormally closed switch 142 in series with the tong dog safety switch146. In this manner the electric circuit of the forward relay coil 120is completed only through the hook dog safety switch 134, thus causingthe forward movement of the knee to be arrested at a still fartherretracted position, at which the extended hook dog does not enter thesaw line.

Tapering of the knee is achieved by depressing the taper push buttonswitch 174 which closes an electric circuit from line L'1 through thetaper feed safety switch 176 and taper release push button 178, throughthe Taper On solenoid 180 to line L-2. This solenoid actuates the aircontrol valve 182 to the position in which air is admitted to the tapercylinder 60 in the direction to retract the piston rod 62 and thus movethe knee structure forwardly relative to the knee base 30.Simultaneously with the energization of the solenoid 180, the relay 184is energized, thereby closing the normally open switches 186, 1258.Switch 186 provides a holding circuit around the taper push buttonswitch 174, while switch 188 completes a circuit from line L-l throughthe taper switching solenoid 190. This solenoid functions to move thegroup of safety Switches relative to their actuating cams, from theirnormal position-when the knees are not tapered to a position at whichthe safety switches will be actuated earlier than normal, to compensatefor the taper of the knees.

Return of the knees to untapered condition is effected by moving thetaper release push button switch 178 to energize the Taper Off solenoid192 which actuates the air control valve 182 to extend the piston rod 62of the taper cylinder 60,

The mechanical assembly of the safety switches and their actuating cams,as illustrated schematically in FIG- URE 13, may be provided by variousmeans, a preferred arrangement being illustrated in FIGURES 8-12,inclusive. In the embodiment therein illustrated, a housing 194 isformed of a base and side walls, and is adapted to be closed with acover (not shown). Supported transversely through the housing, by meansof bearings 196, is a shaft 198 which, as indicated in FIGURE 13, isadapted to mount a sprocket 200 for receiving the chain 202 trained overa second sprocket 204 mounted on the drive shaft 48 of the set shaftmotor 50.

Mounted at spaced intervals upon the shaft 198 within the housing are aplurality of spaced hubs 20-6, the hubs being secured to the shaft bysuch means as the set screws 208. The lateral ends of the hubs arereduced in diameter, and each receives freely thereon a ring shaped cammember, the six illustrated being identified by reference numerals 210,212, 214, 216, 218 and 220. Each of the ring shaped cam members isreleasably secured to the hub by a diametrically disposed clamp plate222 which is releasably secured to the hub by such means as the bolts224. The thickness of the cam member is made greater than the depth ofthe reduced end section of the hub, whereby the clamp plate functions tofrictionally grip the cam member in any selected position of adjustmenton the hub. In this manner each cam member may be adjusted to anyposition of rotation with respect to the safety switch it operates.

A U-shaped frame is journaled at its free ends 226 on the shaft 198, andthe intermediate section 228 of the frame functions to support theplurality of safety switches 126, 134, 136, 146, 156, 176. In theembodiment illustrated, and as best shown in FIGURES 8 and 11, theintermediate section of the frame is provided with a plurality ofopenings through which project the threaded sleeves 230 of the safetyswitches. A securing nut 232 clamps the switches to the frame, with theroller contact members 234 of the switches disposed in line with thecams for actuation thereby.

The taper switching solenoid 190 is mounted upon the housing above theswitch supporting frame, with its depending armature 236 connectedresiliently to the switch supporting frame 226 by means of the coilspring 238. A second coil spring 240 of lesser strength interconnectsthe switch support frame and the base of the housing, to preventbouncing of the frame when the latter is returned to its normal positionafter elevation by the taper switching solenoid. The limits of movementof the frameare confined adjustably by the abutment screws 242 and 244which are threaded through the opposite inturned ends of the bracket 246secured to the housing. By means of these adjustable abutment screws,the switch supporting frame may be adjusted to any normal position andto any elevated position corre sponding to the desired taper, therebyshifting the position of the safety switch actuating rollers 234 withrespect to the cam lobes on the ring shaped cam members.

From a consideration of FIGURES 2, 3 and 6 of the drawings, it will beapparent that the minimum distance between the front face 58 of the kneeand the saw line 26 will be the least when the tong dogs and hook dogare retracted, as per FIGURE 2; will be greater when the tong dogs areextended and the hook dog retracted;

as per FIGURE 3; and will be greatest when the hook dog is extended, asper FIGURE 6. Accordingly, the switch actuator cams associated with thesafety switches are so adjusted that as the shaft 198 is rotated duringforward travel of the knees, the hook dog safety switch 134 is openedfirst, the tong dog safety switch 146 is openednext, and the forwardlimit safety switch 136 is opened last. This arrangement is illustratedin FIGURE 13.

The hook feed and taper feed safety switches 156 and 176, respectively,are provided in order to prevent extension of the hook dog or taperingof the knees whenever the knees are disposed so close to the saw line 26that extension of the hook dog would bring it across the saw line, ortapering of the knees would bring the knees across the saw line.Accordingly, the cams associated with the safety switches for the hookdogfeed and taper feed are so adjusted that the electric circuits of thehook dog solenoid 166 and taper solenoid are opened when the knees aretoo far forward to permit extension of the hook dog. or tapering of theknees.

The cam 210 is associated with the reverse safety switch 126 is 50arranged as to open the latter when the knees have been retracted totheir maximum limit, as will be apparent.

Referring now to FIGURE 14 of the drawings, the modification illustratedtherein eliminates the pivoted support 226, 228 for the safety switchesand the associated taper switching solenoid assembly of the embodimentillustrated inFlGURES 813 inclusive, and substitutes therefor aplurality of additional safety switches and associated actuating cams.Thus, the physical assembly for the embodiment of FIGURE 14 may beprovided by the structure illustrated in FIGURES 8 and 9, by eliminatingthe solenoid and springs 238, 240 and rendering the switch support frame226, 228 rigid, as by turning the upper abutment screw 242 downwardlyinto engagement with the frame. It will be understood, of course, thatthe switch support frame, housing and shaft 198 will be elongated inorder to accommodate the additional switches and cams illustrated inFIGURE 14. The electrical circuitry for the set shaft motor 50 is thesame as illustrated in FIGURE 13, as is the actuation of the tong dogs,hook dog, and taper. However, the control of forward movement of theknees is as follows:

Under the operating condition illustrated in FIGURE 2, wherein the kneesare not tapered and the dogs are not extended, forward movement of theknees is effected by closing of the forward jog switch 130, or by thesetworks mechanism 132, thereby completing the electric circuit of theforward relay 120 from line L-2, through all of the parallel circuits ofthe safety switches 134, 136, 146, 250, 252, 254 and the associatedswitches 256, 258, 260, 262, 264 of the relays 266, 268, 270, 272, 274respectively, and thence through the emergency stop push button switch128 to line L--1. It will be remembered that when the tong dogs areretracted, by closure of the tong dog push button switch 152, relay 266is energized and the normally open switch 256 is closed. Thus, as theknees progress forwardly, the safety switches are opened successively,until the forward limit safety switch 136 is finally opened by itsassociated cam 214, to break the circuit of the forward relay 120 andde-energize the set shaft motor 50.

Under the conditions illustrated in FIGURE 3, the tong dogs are extendedby opening the push button switch 152. The relay 266 thus isde-energized and hence the forward movement of the knees will bearrested when the tong dog safety switch 146 is opened by associated cam216. Since this occurs earlier than the condition for FIGURE 2, theforward movement of the knees will be arrested before the extended tongdogs reach the saw line 26.

The taper condition illustrated in FIGURE 4 is achieved by closing thetaper push button switch 174 to energize the solenoid 180 as well as therelay 184. Upon enengization of the relay 184, closure of the normallyopen switch 188 completes a circuit from the line L-1 through relay 268to line L-2. This relay causes its associated switch 258 to open, andthus the forward movement of the knees will be arrested when the tapersafety switch is opened by its associated cam 276.

Under the condition illustrated in FIGURE 5, with the knees tapered andthe tong dogs extended, the circuit of relay 270 is completed from lineL-2 through the closed switch 278 of relay 266 and the closed switch 280of the energized relay 268, through the emergency stop push buttonswitch 128 to line L-1. Accordingly, the switch 260 associated withrelay 270 is opened and forward movement of the knees is arrested whenthe taper and tong dog safety switch 252 is opened by its associated cam282.

Under the condition illustrated in FIGURE 6, extension of the hook dogis achieved by energizing the air control valve solenoid 166, asdescribed hereinbefore. This simultaneously energizes relay 170 andcloses its associated switch 172 to complete the electric circuit ofrelay 272. Upon energization of this relay, the normally closed switch262 associated therewith is opened, and hence forward movement of theknees is arrested when the hook safety switch 134 is opened by itsassociated cam 212.

Under the operating condition illustrated in FIGURE 7, wherein the kneesare tapered and the hook dog is extended, energization of relays 268 and272 closes the normally opened switches 280 and 284 associated therewithand thus completes the electric circuit of relay 274 from line L-2through said closed switches, through the emergency stop push button 128to line L-1. With the energization of the relay 274 the switch 264associated therewith is opened and hence forward movement of theknees'is arrested when the taper and hook dog safety switch 254 isopened by its associated cam 286.

As in the modification previously described, means also is provided inthe embodiment of FIGURE 14 to prevent the hook dog from being extendedand the knees from being tapered when the knee is positioned too closeto the saw line. Thus, the source of electric potential for the hook dogactuating relay 158 extends from line L-2 through said relay 158,through the hook dog push button switch 154, through the normally closedswitch 288 of relay 290, and thence through the hook feed safety switch156 associated with the cam 218 to line L1. In the event the knees havebeen tapered, energization of relay 184 closes the normally open switch188 and completes the electric circuit of relay 290. Thus, the electriccircuit through the hook feed safety switch is broken and the electriccircuit for the hook actuator relay then must come from line L-1 throughthe taper and hook feed safety switch 292 and the closed position innormally open switch 294.

The electric potential for the taper solenoid 180 is supplied from theline L1 through the taper feed safety switch 176, the normally closedswitch 296 of relay 298, through the taper release push button 178 andthe closed taper push button switch 174. However, in the event the hookdog has been extended prior to tapering of the knees, the energizationof relay and the closing of its associated switch contact 172, causesenergization of relay 298. This opens the normally closed switch 296 andcloses the normally open switch 300. Hence, electrical potential for thetaper solenoid then must pass from line L-l through the taper and hookfeed safety switch 292 and thence through the closed switch 300. Thus,if it is desired to extend the hook dog when the knees are tapered, orif it is desired to taper the knees while the hook dog is extended, theelectric supply for either of these must come through the taper and hookdog feed safety switch 292 which is controlled by the associated cam302.

In order to maintain a taper, by keeping relay 184 energized, whileretracting the hook dog from its extended position, relay 290 isprovided with a third switch 304 which, when closed, by-passes to lineL-l the switches 296 and 300 of relay 298. Thus, relay 184 is maintainedenergized through switch 304 during reversion of the switches 296 and360 when relay 298 is de-ener gized upon opening of the hook push buttonswitch 154.

It is believed to be apparent from the foregoing description that thepresent invention effectively and economically provides for completesafety ofoperation of the components of a sawmill carriage, bypreventing under any circumstances the projection of any of saidcomponents into the saw line. The safety system is readily adaptable toall types of carriages and does not interfere with nor modify theoperational procedure of the carriage assembly.

It will be apparent to those skilled in the art that various changes inthe details of construction described and illustrated herein may be madewithout departing from the scope and spirit of this invention. Forexample, it will be understood that the safety system relating to thehook dog may be duplicated for additional dogs, or may be modified tooperate in conjunction with a plurality of hook dogs. Although the tapersystem described hereinbefore provides but a single taper control pushbutton switch and associated elements to provide a single magnitude oftaper, it will be understood that the multiple controls normallyprovided on a sawmill carriage for tapering the knees to variousmagnitudes and directions, may be associated with the safety system ofthis invention, either through a single taper safety assembly or throughmultiple taper safety assemblies, each related to a given magnitude oftaper.

Further, as explained hereinbefore, the prime mover for the knees may beof the rectilinear type such as bydraulic rams, instead of the rotarytype employed with the rotary set shaft illustrated. In such event, itwill be understood that the rotary cam and shaft arrangement illustratedmay be replaced by a cam system which is operable by rectilinear motion.Still further, the function of the safety switches and associated camsmay be provided by other means, such as electrical potential matchingsysterns which function, upon achieving a potential match at apredetermined point of forward movement of the knees, to open theelectric circuit of the forward relay 120.

The safety system of this invention is adaptable for use with apparatusother than sawmill carriages. Thus, the reciprocable knee structure 52accommodating taper, and the reciprocable tong and hook dogs, may havetheir counterparts in other apparatus wherein reciprocable members aremovable selectively with respect to a reference point.

The foregoing and other changes may be made, and therefore it is to beunderstood that the foregoing description is primarily illustrative ofthe invention and does not define the scope of the appended claims.

Having now described my invention and the manner in which the same maybe used, what I claim as new and desire to secure by Letters Patent is:

1. For use with apparatus having a support assembly reciprocablerelative to a reference point, and electrically actuated first drivemeans therefor, the support assembly including a plurality ofreciprocable members, and elec trically actuated drive means forreciprocating each member between extended and retracted positionsrelative to the reference point independently of the first drive means:safety means for preventing extension across the reference point of saidreciprocable members, said safety means comprising switch means in thecircuit of the first drive means actuator, and switch actuator meansoperatively associated with the said reciproc-abl-e members of thesupport assembly and operable by the first drive means for actuating theswitch means [when the forwardmost one of the said reciprocable membersreaches a predetermined position relative to the reference point,whereby to stop the movement of the support assembly toward thereference point] and stopping the movement of the support assemblytoward the reference point when at least one of the reciprocable membersis in extended position and the forwardmost one of said extended membersreaches a predetermined position short of the reference point.

2. The safety means of claim 1 including switch means in each of thecircuits of the actuators for the reciprocable members, and switchactuator means operatively associated with each of the correspondingreciprocable members of the support assembly and operable by the firstdrive means for actuating the switch means and deactivating theassociated recipro'cable member actuator when the support assembly is sopositioned relative to the reference point that subsequent extension ofthe retracted reciprocable members would bring said members across thereference point. v s

3. For use with apparatus having a support assembly reciprocablerelative to a reference point, and electrically actuated first drivemeans therefor, the support assembly including a plurality ofreciprocable members, and electrically actuated drive means forreciprocating each member between extended and retracted positionsrelative to the reference point independently of the first drive means:safety means for preventing extension across the reference point of saidreciprocable members, said safety means comprising a plurality f switchmeans in the circuit of the first drive meansactuator and eachoperatively associated with one of said recip-rocable members, and aplurality of switch actuator means each operatively associated with oneof the said reciprocable members of the '10 members is in extendedposition and the forwardmost one of said extended members reaches avpredetermined position short of the reference point.

4. For use with a sawmill carriage having a knee assembly reciprocalrelative to a saw line, and electrically actuated first drive meanstherefor, the knee assembly in? cluding a plurality of reciprocablelog-engaging members, and electrically actuated drive means forreciprocating each log-engaging member between extended and retractedpositions relative to the saw line independently of the first drivemeans: safety means for preventing extension across the saw line of saidreciprocable log, engaging members, said safety means comprising switchmeans in the circuit of the first drive means actuator, and switchactuator means operatively associated with the said reciprocablelog-engaging members of the knee assembly and operable by the firstdrive means for actuating the switch means [when the forwardmos-t' oneof the said reciprocable log-engaging members reaches a predeterminedposition relative to the saw line, whereby to stop the movement of theknee assembly toward the saw line] andszopping the movement of the kneeassem bly toward the saw line when at least one of the reciprocablemembers is in extended position and the forwardmost one of said extendedmembers reaches a predetermined position short of the saw line.

5. The safety means of claim 4 including switch means in each of thecircuits of the actuators for the reciprocable members, and switchactuator means operatively associated with each of the correspondingreciproc-able mem bers of the knee assembly and operable by the firstdrive means for actuating the switch means and deactivating theassociated reciprocable member actuator when the knee assembly is sopositioned relative to the saw line that subsequent extension of theretracted reciprocable members would bring said members across the sawline.

6. For use with a sawmill carriage having a knee assembly reciprocablerelative to a saw line, and electrically actuated first drive meanstherefor, the knee assembly including a plurality of reciprocablelog-engaging members, and electrically actuated drive means forreciprocating each log-engaging member between extended and retralctedpositions relative to the saw line independently of the first drivemeans; safety means for preventing extension across the saw line of saidreciprocable logengaging members, said safety meanseomprising aplurality of switch means in the circuit of the first drive meansactuator and each operatively associated with one of said recipnocablelog-engaging members, and a plurality of switch actuator means eachoperatively associated with one of the said reciprocable log-engagingmembers of the knee assembly and operable by the first drive means foractuating the switch means [associated with the forwardmost one of thesaid reciprocable log-engaging members when the latter reaches apredetermined position relative to the :saw line, whereby to stop themovement of the sembly reciprocable relative to a saw line, andelectrically actuated first drive means therefor, the knee assemblyincluding a plurality of reciprocable log-engaging members, andelectrically actuated drive means for reciprocating each log-engagingmember between extended and retracted positions relative to the sawlineindependenlty of theffir st drive means: safety means forpreventingextension across the saw line of said reciprocable logengaging members,said safety means comprising switch means in the circuit of the firstdrive means actuator, switch actuator means, and means operable by thefirst drive means for moving the switch means and switch actuator meansrelative to each other, the switch actuator means functioning uponengagement with the switch means [associated with the forwardmost one ofthe said reciprocable log-engaging members when the latter reaches apredetermined position relative to the saw line, to actuate the switchmeans whereby to stop the movement of the knee assembly toward the sawline] to stop the movement of the knee assembly toward the saw line whenat least one of the reciprocable members is in extended position and theforwardmost one of said extended members reaches a predeterminedposition short of the saw line.

8. For use with a sawmill carriage having a knee assembly reciprocablerelative to a saw line, and electrically actuated first drive meanstherefor, the knee assembly including a reciprocable log-engagingmember, electrically actuated second drive means for reciprocating thelogengaging member between extended and retracted positions relative tothe saw line independently of the first drive means for tapering saidlog-engaging member, a reciprocable dog member on the log-engagingmember, and electrically actuated third drive means for reciprocatingthe dog member relative to the saw line: safety means for preventingextension across the saw line of said reciprocable log-engaging memberand dog member, said safety means comprising switch means in the circuitof the first drive means actuator, and switch actuator means operativelyassociated with the said reciprocable members of the support assemblyand operable by the first drive means for actuating the switch means[when the forwardmost one of the said reciprocable members reaches apredetermined position relative to the saw line,

vwhereby to stop the movement of the knee assembly toward the saw line]and stoppingthe movement of the knee assembly toward the saw line whenat least one of the reciprocable members is in extended position and theforwardmost one of said extended members reaches a predeterminedposition short of the saw line.

9. For use with a sawmill carriage having a knee assembly reciprocableto a saw line, and electrically actuated first drive means therefor, theknee assembly including a reciprocable log-engaging member, electricallyactuated second drive means for reciprocating the log-engaging memberbetween extended and retracted positions relative to the saw lineindependently of the first drive means for tapering said log-engagingmember, reciprocab le dog members on the log-engaging member, andelectrically actuated drive means for reciprocating each dog memberindependently relative to the saw line: safety means for preventingextension across the saw line of said reciprocable log-engaging memberand dog members, said safety means comprising a plurality of switchmeans in the circuit of the first drive means actuator and eachoperatively associated with one of said reciprocable members, and aplurality of switch actuator means each operatively associated with oneof the said reciprocable members of the knee assembly and operable bythe first drive means for actuating the switch means [associated withthe forwardmost one of the said reciprocable members when the latterreaches a predetermined position relative to the saw line, whereby tostop the movement of the knee assembly toward the saw line] and stoppingthe movement of the knee assembly toward the saw line when at least oneof the reciprocable members is in extended position and the forwardmosttone of said extended members reaches a predetermined position short ofthe saw line.

10. The safety means of claim 9 including switch means in each of thecircuits of the reciprocable taper and dog drive means actuators, andswitch actuator means operatively associated with each of thecorresponding reciprocable members of the knee assembly and operable bythe first drive means for actuating the switch means and deactivatingthe associated reciprocable member actuator when the knee assembly is sopositioned relative to the saw line that subsequent forward tapering ofthe logengaging member and extension of the retracted dog members wouldbring said members across the saw line.

11. For use with apparatus having a support assembly reciprocablerelative to a reference point, and electrically actuated first drivemeans therefor, the support assembly including a reciprocable member,and electrically actuated drive means for reciprocating said memberbetween extended and retracted positions relative to the reference pointindependently of the first drive means: safety means for preventingextension across the reference point of said reciprocable member, saidsafety means comprising switch means in the circuit of the first drivemeans actuator, and switch actuator means operatively associated withthe said reciprocable member of the support assembly and operable by thefirst drive means for actuating the switch means and stopping themovement of the support assembly toward the reference point when thereciproca' ble member is in extended position and reaches a predetermined position short of the reference point.

12. The safety means of claim 11 including switch means in the circuitof the actuator for the reciprocable member, and switch actuator meansoperatively associated with the reciprocable member of the supportassembly and operable by the first drive means for actuating the switchmeans and deactivating the reciprocable member actuator when the supportassembly is so positioned relative to the reference point thatsubsequent extension of the retracted reciprocable member would bringsaid member across the reference point.

13. For use with a sawmill carriage having a knee assembly reciprocablerelative to a saw line, and electrically actuated first drive meanstherefor, the knee assembly including a reciprocable log-engagingmember, and electrically actuated drive means for reciprocating thelogengaging member between extended and retracted positions relative tothe saw line independently of the first drive means: safety means forpreventing extension acr oss the saw line of said reciprocablelog-engaging member, said safety means comprising switch means in thecircuit of the first drive means actuator, and switch actuator meansoperatively associated with the said reciprocable logengaging member ofthe knee assembly and operable by the first drive means for actuatingthe switch means and stopping the movement of the knee assembly towardthe saw line when the reciprocable member is in extended position andreaches a predetermined position short of the saw line. 1

14. The safety means of claim 13 including switch means in the circuitof the actuator for the reciprocable log-engaging member, and switchactuator means operatively associated with the reciprocable log-engagingmember and operable by the first drive means for actuating the switchmeans and deactivating the reciprocable member actuator when the kneeassembly is so positioned relative to the saw line that subsequentextension of the retracted reciprocable log-engaging member would bringsaid member across the saw line.

References Cited in the file of this patent or the original patent 3UNITED STATES PATENTS 1,725,861 Grueter Aug. 27, 1929 1,846,621 TannerFeb. 23, 1932 2,466,776 May Apr. 12, 1949 2,661,779 Saunders n Dec. 8,1953 2,721,588 Roberts Oct. 25, 1955 2,807,293 Smith et al. Sept. 24,1957

